With a week left to act, agricultural leaders in Congress are still deadlocked on two major issues for a new U.S. farm bill, cuts in crop subsidies and reductions in food stamps, said two of the four key negotiators on Thursday.

But the leaders of the House and Senate agriculture committees suggested that recent talks had yielded at least some progress. Agriculture Secretary Tom Vilsack urged prompt passage of the new bill.

Without reauthorization, U.S. farm policy would revert to the provisions of the Agricultural Act of 1949, the last "permanent" farm bill and one crafted for an entirely different U.S. economy.

Among other things, if lawmakers do not agree on a new bill, milk prices in U.S. grocery stores could double next month under terms of the fall-back statute which would also limit crop plantings while pushing up farm subsidies by billions of dollars.

A new farm bill would now likely be absorbed into an overall budget-cutting bill that could avert the looming "fiscal cliff" of tax increases and spending cuts. Farm spending cuts of $23 billion to $35 billion have been floated.

In speeches at a farm policy conference in Washington, the leaders of the House and Senate Agriculture committees were adamant the final version of the five-year, $500 billion bill must include elements that are lightning rods for controversy.

Congress is scheduled to adjourn for the year on Dec. 14, although top Republicans have said it will not adjourn until a solution to the fiscal cliff has been announced.

"I would rather have nothing" than a farm bill that does not give farmers the option of price supports, said House Agriculture chairman Frank Lucas. "You need to give our producers a choice."

The Senate version of the farm bill, passed in June with proposed spending cuts totaling $23 billion, would replace traditional farm subsidies with an insurance-like program that compensates grain and oilseed growers when revenue from a crop is more than 11 percent below average.